Compass



5 3-364 ilk 7 s 069 9 065 SR Jan. 26, 1937. J 1 HAND 2,069,065

COMPASS Filed March 9. 1935 33| GtUNEinipfiL Hi nun"...

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Patented Jan. 26, 1937 UNITED STATES PATENT OFFICE 1 Claim.

The present invention relates to compasses with more particular reference to a compass having two chambers, one a card chamber, completely filled with damping liquid and pivotally supporting the compass card in oil or other suitable retarding or damping liquid and the other an expansion chamber for accommodating changes in the quantity of oil or other liquid completely filling the card chamber so as to permit fiow between due to thermal changes.

A purpose of the invention is to provide a compass of the kind indicated that will be adapted to easy and inexpensive manufacture and well suited to the needs of service.

A further purpose is to make a compass of the kind indicated with the card and expansion chambers in a relatively rigid unit having normally submerged communication between the chambers.

A further purpose is to guard the card chamber of a compass of the type indicated from the entry into it of bubbles of air with the resultant upset in the reliability and proper operation of the compass.

A further purpose is to screen or shield the card chamber from access of air from the expansion chamber while permitting such gradual passage of sealing liquid from either chamber to the other as will properly accommodate the need for changes in the mass of liquid filling the card chamber due to thermal changes within the card chamber.

A further purpose is to close the inlet to the card chamber from an expansion chamber with porous material naturally absorbent with respect to the liquid within the chambers, permitting the passage of liquid from chamber to chamber while sealing the chambers one from the other with respect to the passage of air and preventing rapid fiow between.

A further purpose is to continuously plug the normally submerged opening between the card and expansion chambers of a compass of the kind indicated with capillary material, continuously filling the capillaries with liquid to permit interchange of liquid between the chambers while sealing the card chamber from air bubbles out of the expansion chamber.

A further purpose is to lessen or eliminate surging of liquid in the expansion chamber incident to vibration disturbances of the compass.

Further purposes will appear in the specification and in the claim.

I have preferred to illustrate one main form only of my invention showing however a number of modifications and selecting a main form and modifications thereof that are practical and efficient in operation and which well illustrate the principles involved.

Figure 1 is a central vertical section of a desirable embodiment of my invention.

Figures 2, 3, 4, and 6 are fragmentary central sections illustrating somewhat different forms.

Figure 5 is a side elevation partly in vertical section to illustrate that the form of the chambers may be varied widely, the illustrated forms, however, being two only of the many forms well suited to the intended use.

Describing in illustration and not in limitation and referring to the drawing:

In the structure of Figure 1 the compass box includes a rigid unit divided into a card chamber l0 and an expansion chamber l l communicating at l2 with the card chamber. The box is formed by rigidly connected shells l3 and i4 secured against leakage at 15. The card chamber is closed by a glass I6 held tightly against a gasket H by a cap I 8 spun beneath a flange is of the shell I3.

The card 20 is provided with usual or suitable magnets 2| and carries a downwardly directed conical cup bearing 22 that supports the card upon a pivot 23. The pivot 23 is connected by post 24 extending upwardly from a base 25 shown rigidly fastened at 26 to the shell H. 3

The base 25 is spaced some distance above and across the opening I2, is suitably open at 21 and provides a preferably downwardly tapering compartment well adapted to receive and hold porous material 28, the interstices of which are completely filled with the damping liquid within the chambers.

Damping liquids of the character intended are very well known and difier in kind and also in relative viscosity according to well known principles. It is not the intention here to alter the character of clamping liquid and the present invention is suitable for the range of liquids used for such a purpose.

The damping liquid is intended not only to fill the card chamber completely but to fill the expansion chamber to such a height that the communicating passage between the card chamber and expansion chamber will be submerged by this liquid no matter how the compass may be tilted or turned.

In the illustrations this is accomplished by projecting the bottom of the card chamber downwardly into the opening (the direction being taken from normal operating compass position) and filling the compass shell so that the expansion chamber is filled well above the communicating opening.

The shapes of the casings I3 and H are such that when the compass is tilted or turned upside down this quantity of liquid continues to fill the chambers above the communicating opening between them.

The shell members l3 and I 4 are preferably formed of spun sheet metal or of molded plastic material and in the assembled compass box connect coaxially at upper peripheral flanges.

The glass, packing and the flanges of the two shells I3 and I4 may be held together by the cup to secure the glass and effect the seal between the two flanges and a space 29 may be formed (see Figure 1) between the two shells to add to the expansion chamber space. In Figure 5 this annular space 29 does not appear.

The bottom of the outer shell is upwardly and inwardly domed at 30 in order to provide for a filling recess 31 opening into the outer shell above the bottom of the shell. In order to provide suitable closure for this securing opening a nut 32 is secured within the dome in line with the recess. The nut or the nut combined with the metal of the dome receives a threaded plug 33 by which the recess may be closed. The plug is sealed by a gasket 34.

When the plug is in place it, along with the adjoining interior dome surface, afiords a support for the porous material 28 which may desirably be filtering material, quite acceptably in the form of wicking. Very excellent results have been obtained by materials which contain capillary tubes which when wet by the damping liquids trap the air and block rapid liquid movement while permitting slow liquid breathing of the card chamber as the liquid expands or contracts.

Though the card chamber is completely filled with damping liquid the expansion chamber is but partially filled with the damping liquid, as normally to some line 35 with an air space 36 above the liquid. The elevation of the line 35 is variant with temperature, principally according to the variance of temperature, with a resultant accommodating flow of liquid between the chambers. Any air bubbles entering the card chamber would seriously afiect the proper operation of the compass.

Conditions of use may subject the whole compass box to simultaneous inward flow out of the expansion chamber to the card chamber (as from a sudden drop in temperature) and such vibratory disturbances as from choppy seas may beat up the air and liquid.

The liquid within the expansion chamber may then become so much disturbed by reason of relatively violent oscillations of the whole box that the liquid entraps small bubbles of air and it is difiicult to prevent some of these bubbles from entering the card chamber. Important features of my invention are directed to the prevention 01 this undesirable condition.

In the form shown in Figure 1, the inner and outer shell members and the glass with the card are assembled without liquid. The screw plug 33 is removed, the compass box inverted and the right amount of liquid for damping oscillations of the card is poured in, completely filling the inverted card chamber and filling the expansion chamber suitably to a point that may optionally be determined by filling at a predetermined temperature preferably to a line 31 even with the inner lip 38 of the expansion chamber.

I now insert into the open end of the expansion chamber the filter or screen 28 of porous material, preferably such as is strongly absorbent with respect to the damping liquid used. The screw plug 33 is now put back after which the compass may be slowly turned over right side up to the position shown in Figure 1.

The porous material is now normally completely submerged in the damping liquid and permits such passage of liquid between the expansion and card chambers as is needed to accommodate thermal changes but refuses passage to, filters out as it were, bubbles of air that may, particularly during choppy sea conditions, come against the sides of the filter or screen even though the filter or screen is normally submerged in the damping liquid.

In Figure 2 the absorbent material 28' surrounds a stem portion 39 of the metal screw 33'. This absorbent plug, optionally circular wicking or fabric wrapped round and round the stem, and which may be desirably somewhat tapered, has a length sufficiently great to have its inward end inserted in the opening l2 of the card chamber prior to the screwing in of the screw 33. When the screw 33 is inserted the stem expands the annular wicking or other suitably porous material, tightening it against the edge of the opening I 2 and provides efiective seal against the entry of air momentarily presented by bubbles of air entrained in the liquid of the expansion chamber during periods of relatively violent disturbance at the compass.

In the form shown in Figure 3 the opening I2 of the expansion chamber receives the end of the metal tube 40. The tube 40 makes an air sealing fit with the edge of the opening l2 of the expansion chamber and presents its lower end to absorbent or porous material 28 inside the cup closure 4| of the expansion chamber. As shown the entire tube must be filled with liquid and the porous material saturated before the parts are sealed to avoid trapping air in the tube or feeding air to the tube from the porous material.

The passage of liquid between the expansion and card chambers to accommodate the thermal changes is through the tube and the packing or other absorbent material at 28 at the lower end of the tube.

As illustrated in Figure 4 I may fill the space between the outer and inner members l3 and H with porous material 42 such as cotton for example preferably also inserting a porous seal 28 across or in the opening I2 between the inner and outer chambers.

The advantage of thus filling the expansion chamber with cotton or other suitable material lies principally in eliminating or greatly lessening such surging movement of the damping liquid as may in choppy seas or the like result in particles of air becoming mingled in the liquid. Here again, the material 42 is desirably well soaked in the liquid before the parts are put together so as to avoid soaking-up of the liquid in it subsequently with resultant later shortage of liquid.

In Figure 1 I show the inner and outer shells 33. GEUMETRICAL lNSTRUMENTS.

optionally much like that in Figure 1. It will be seen the box units of Figures 1 and 5 are generally alike except that the annular expansion space between the two members of Figure 1 has been omitted in Figure 5, because the members connect together intermediate the height of the outer member at 43.

In Figure 6 the shell members l3, H are of dififerent shape and the pivoting of a difierent character. The post 24 supports a jewel 44 and a bell 45 within which bell 45 a bell 46 is located secured to the pivot pin 23 connected with the card.

The number of porous materials which act as a filter for air bubbles while allowing passage of oil, alcohol or other damping liquid is quite large and I have therefore made no attempt to give a. complete list, preferring to rest upon a clear statement of the function and several examples, among which might be given a sponge base with a coating of fabric about it to be used in the position of Figure 1 for example. The sponge gives a resilient filling material for the filter and the extent of filtering may be varied widely as desired by the thickness of the cloth, tightness or looseness of the weave, number of layers, etc., to give complete filtering against air bubbles along with just the right retardation against undue speed of liquid flow, into which, of course, the different viscosities of permissible damping material will of course enter.

It will be evident that my air-bubble-filtering protection between the two chambers has an advantage not only in connection with the convenient and eiTective arrangement and confirmation of the two chambers but in any relation in which it is desirable to maintain the card chamber of a compass free from air.

It will be further evident that though the placing of the expansion chamber upon the bottom as shown is quite a convenience in a top reading gimballed compass and greatly improves the appearance and symmetry of any compass it is not essential to the application of the principles of my invention which in its broader interpretation may be carried out without regard to the location of the expansion chamber. This is especially true where the compass is not gimballed.

In view of my invention and disclosure, variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art to obtain all or part of the benefits of my invention without copying the structure shown and I therefore claim all such in so far as they fall within the reasonable spirit and scope of my invention.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

In a compass of the type indicated, a compass box comprising a card chamber having an opening at a low part of the chamber, an expansion chamber communicating with the card chamber through the opening, and damping liquid completely filling the card chamber and opening and partially filling the expansion chamber to a depth above the opening, the card and expansion chambers comprising coaxial cup members having upper peripheral flanges mating together, a packing ring upon the flange of the upper member, a glass upon the packing ring and means for clamping the glass and packing ring and peripheral flanges together.

JOHN L. H. HAND. 

